Terminal Conditional Handover Timer Management

Solution Overview

Problem

In Conditional HO procedures, terminals do not receive handover commands, leading to potential delays in cell transitions due to unstarted handover timers, even when radio link failures occur.

Innovation Solution

A terminal is equipped with a receiving unit to obtain configuration information for a transition destination cell and a control unit that starts a timer upon receiving this information, allowing the terminal to perform a conditional cell transition before the timer expires without waiting for a transition command.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the terminal performs conditional cell transition without receiving a handover command, then the cell transition speed is improved and radio link interruption is avoided, but the handover timer is not started which may cause delayed transition attempts when radio link failure occurs

Engineering Contradiction:

Improvecell transition speedVSAvoidtransition delay

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The terminal starts the handover timer in advance when receiving configuration information from the source cell, before actually executing the conditional handover to the target cell. This preliminary action ensures that the timer is running and will trigger appropriate actions if the handover is not completed in time, while still allowing the terminal to transition without waiting for a handover command.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts the handover timer behavior based on the conditional handover state. The timer is started when configuration information is received and can be stopped or reset when the conditional handover is successfully executed or when the transition condition is met, allowing flexible time management throughout the handover process.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the terminal waits for a handover command before transitioning, then the handover timer can be started to control the transition process, but the cell transition speed decreases and radio link interruption occurs

Engineering Contradiction:

Improvehandover control reliabilityVSAvoidcell transition speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The terminal starts the handover timer in advance when receiving configuration information from the source cell, before actually executing the conditional handover to the target cell. This preliminary action ensures that the timer is running and will trigger appropriate actions if the handover is not completed in time, while still allowing the terminal to transition without waiting for a handover command.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses the handover timer as a feedback mechanism to monitor whether the conditional handover is proceeding normally. If the timer expires before the handover is completed, it indicates a problem and triggers appropriate error handling, providing reliability control while allowing fast transition when conditions are met.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS12213016B2Terminal

Publication Date: 2025.01.28 NTT DOCOMO INC

AI summary

A terminal includes a receiving unit that receives configuration information of a transition destination cell from a gNB by a conditional cell transition in the gNB in which the terminal resides, and a control unit that performs a transition to the transition destination cell based on the configuration information of the transition destination cell, without receiving a transition command. In a case where the receiving unit receives the configuration information of the transition destination cell, the control unit starts a CHO timer and can perform the conditional cell transition before the CHO timer expires.